It is often desired to modify the trajectory of a projectile (including missiles) after it has been fired. Conditions such as wind, temperature variations, precipitation, aiming error etc. can cause the projectile to deviate from its intended course, as determined by remote tracking of the projectile or on-board guidance systems. To modify the trajectory, mechanisms are used which are fit onto the projectile and deploy aerodynamic tabs, or fins, while in flight, to impart a corrective action to the projectile. Such corrective action may consist of braking, spin modulation and deflection of the projectile, each action being achieved by a single independent mechanism.
Such mechanisms utilize fins which pivot or eject from a closed inboard position to an open position whereby they extend radially around the projectile body. The pivoting means are subject to breakage when deployed into the airstream and in order to prevent such breakage the fins and pivots must be relatively massive and are typically of heavy machined metal. When deployed as a braking mechanism, the fins become spaced apart so as to present voids between fins, which require the fins to be larger to compensate for the voids. In one embodiment of the present invention an arrangement is provided which presents a continuous fin surface around the periphery of the projectile, with light-weight fins, to increase effective fin area and thus enhance braking action.
In other types of flight altering mechanisms, fins are deployed to spin modulate or deflect the projectile. They cannot, however, apply a braking action without deploying a second independent mechanism. In other embodiments of the present invention arrangements are provided that can selectively and sequentially accomplish spin modification, deflection, as well as braking as a final adjustment, if required.